Amplifying system



Dec. 18,1923. 11,477,898

C. W. RICE AMPLIFYING SYSTEM Filed Feb. 11, 1919 I'l'l'l'l'lLl'l M I I I I I l l l lw l l l l l l l i'l'l'l'l'l'l'l'l'I'l'l'i'l Inventor:

Che terWRice,

His Attorney.

Patented Dec. lit), i923."

warren stares @FFHCZE.

CHESTER W. RICE, F SGHENECTADY,'NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC 1 COMPANY, A CORPORATION OF NEW YORK.

AMPLIFYING SYSTEM.

Application filed February 11, 1919. Serial No. 276,399.

To all whom it may concem: grid circuits of the succeeding amplifiers in Be it known that I, CHESTER W. Bron, a substantially undirninished amplitude while citizen of the United States, residing at the potential variations of difi'erent frequen- Schenectady, in the county of Schenectady, cies occurring in the plate circuits Will be a State of New York, have invented certain applied to the grid circuits in greatly reneW and useful Improvements in Amplifyduced amplitude.- ing Systems, of which thefollowing is a lnmy prior application above referred to, specification. I have in certain cases applied the potential y present invention relates to the amplivariations produced in the plate circuits to 101fication of electric currents of small intenthe grid circuits of the succeeding amplifiers sity, and more particularly to the amplificaby means of shunt connections between the tion of high'frequency currents used for sigcathodes and anodes of the amplifiers, which naling purposes. One of the objects of my shunt connections comprise a resistance in invention is to provide an efficient system series with a capacity, the potential varia- 15 for amplifying small currents of a articution across the resistance being the operatlar desired frequency Without at tfib same ing potential which is applied to the grid time. amplifying currents of other frequencircuit of the succeeding amplifier. A. concies to any appreciable extent. nection of this kind is useful for accomplishln carryin my invention into effect, l eming the purposes of the present invention in 20 ploy a plura ity of electron discharge relays that the condenser ofi'ers a high impedance or amplifiers, preferably of the high vacuum to low frequency current and a low impedor pliotron type, and connect these relays in ance to high frequency currents. As a recascade. The plate circuits in all of these sult the greater percentage of thedrop of amplifiers are supplied with current from a potential in the circuit produced by h gh 2 common source and a high resistance is infrequency currents occurs across the res stv inserted in each plate circuit. The electric ance, and it is therefore effective upon the current which is to be amplified is applied grid of the succeeding amplifier. F or low to the grid circuit of the first amplifier of frequency currents, however, the greater the series and the current in the plate circuit proportion of the drop in potentlal occurs in of that amplifier is varied in accordance across the condenser, and this drop in pcwith the well known operation of amplifiers tential has no efl'ect upon the grid circult of of the type mentioned. As a result there the succeeding amplifier. will be a variation in the potential diifer- I have also in one case in the above menence between the cathode and anode of the tioned application shown a modification 1n :5 amplifier and these potential variations are which the shunt circuit mentioned 15 made applied to the grid circuit of the second up of a condenser in series with a combmaamplifier. The variable potential between tion of inductance and capacity 1n parallel, the cathode and anode of the second amwhich is resonant to the frequency of the plifier is in turn applied to the grid circuit currents which it is desired to amplify. This of the third amplifier, and so on'throughout combination is more efi'ective as a wave filthe series. The plate circuit of the last amter because of the fact that the capacity and plifier includes a telephone receiver or other inductance in parallel offer an extremely device for giving the desired indication of high impedance to currents of one part1cuthe amplified currents. lar frequency and a much lower impedance Ina rior application, Serial No. 183,785, to every other frequency either higher or filed Ju y 31, 1917, I have described a syslower than the desired frequency. 1

tem having theigeneral.characteristics point- In my application mentioned above, I ed out above. n obtaining the object of my have claimed specifically the connection 1n present invention, provide what are now which the shunt circuit is made up of capaccommonly known in the art as filtering conity and resistance, but I have not claimed nections between the successive amplifiers of broadly the use of a Wave filtering connecthe series for selecting from the'plate cirtion between the successive amplifiers. cuits potential variations of a certain de- My present invention Wlll best be undersired frequency and applying these to the stood by reference to the followlng descr1p with the different cathodes allowing tion taken in connection with the accompanying drawing which shows a diagrammatic representation of circuit connections which may be employed in carrying my invention into effect.

As indicated in the drawing. an antenna 1 is connected by means of the usual inductive coupling :2 to the grid circuit of the amplifier The plate circuit of this amplifier. as well as the plate circuits of amplifiers 1. 5 and 6. is supplied with current from the battery T. from this battery at S the filamentary cathodes of the amplifiers are supplied with heating current atthe proper voltage. variable resistances 9. 10. 11. and 12. in series fointhe adjustment of the temperature of each cathode independently of the others. In the plate circuits of amplifiers 3. t. 5 and 6. I insert high resistances 13. 11. 15 and 16. hen current is received in the antenna the potential of the grid of amplifier 3 is varied and the current through the amplifier is varied accordingly. As a result the potential of the anode of the amplifier varies with respect to the cathode. In order to impress this potential variation upon the grid circuit of amplifier 4. a shunt circuit is provided between the cathode and anode of amplifier 3. which comprises a condenser 17 in series with a variable condenser 18 and an inductance 19 in parallel. The grid of amplifier J is connected to a point between the condenser 17 and the condenser 18 and inductance 19. As a result the potential variations across the combination of condenser 18 and inductance 19 are effective in the grid circuit of amplifier 41. The condenser 17 offers a comparatively low impedance to the high frequency currents while the combination of condenser 18 and inductance. 19 offers a very high impedance to currents of the frequency for which this combination is resonant. If, therefore. this combination is tuned to the frequency of the currents which it is desired to amplify, the greater portion of the potential drop in the shunt circuit for currents of the desired fre quency will be effective upon the grid circuit of amplifier 4. Condenser 17 offers a very high impedance to low frequency currents and hence the greater proportion of the potential drop for low frequency currents through the shunt circuit will occur across the terminals of condenser 17 and these low frequency potential variations will be impressed upon the rid circuit of amplifier 4 in greatly reduced amplitude. The combination of condenser 18 and inductance 19 offers a muchlower impedance to currents of greater frequency than to currents of the desired frequency. and therefore the amplitude of potential variations of higher fre uency with respect to those of the desire fre- By means of a tapquency will also be greatly reduced in the grid circuit of amplifier 4. 4

Thus it will appear that the arrangement which I have shown is highly selective to potential variations of the desired frequency and permits the amplification of these potential variations without producing any great amplification of potential variations of other frequencies. This arrangement is of particular value where it is desired to secure a high amplification of a particular high frequency without at the same time amplifying currents of other frequencies which may be impressed upon the system or which may be produced therein by reason of the action of the apparatus. The resultin potential variations between the cathode and anode of amplifier 4 are imprcssed'npon the grid circuit of amplifier 5 in the same manner as that which has just been described by means of a similar shunt circuit made up of condenser 20 and variable condenser 21 and inductance 22 in parallel. The potential variations set up between the cathode and anode of amplifier 5 are in turn impressed upon the grid circuit of amplifier 6 in the same manner.

While I have indicated only four amplifiers thus connected in cascade, as many amplifiers as desired or as ma be necessary to secure the desired degree 0 amplification may be thus connected. In the present case the variable potential between the cathode are transmitted by ,means of continuous waves local oscillations for receiving by the heterodyne method may be produced by the electron discharge generator 25, connected as shown. so as to impress local oscillations upon the circuit which includes the telephone receiver 24.

\Vhile I have shown and described a filtering connection made up of a condenser in series with an inductance and capacity in parallel, my invention is not limited to this particular connection as in my claims which call broadly for a filtering connection -I mean to include a connection of the type described in my prior application which is made up of a condenser with a high resistance in series therewith. It will be apparent also that my broad claims are not limited to the use of either one of these connections to the exclusion of the other as both forms of connection may be employed in the same amplifying system. It is also apparent that many other modifications in the particular connections used and in the specifi use to which my invention is applie may be made without departing from the scope of my invention as set forth in the appended claims.

iii

aeraeee What ll claim as new and desire to secure by Letters Patent of the United States, is

1. The combination in an amplifying system of a plurality of electron discharge amplifiers each of which has a cathode, an anode and a grid and plate and grid circuits, means for impressing currents which are to be amplified upon the grid circuit of one of said amplifiers, high ohmic resistances in the plate circuits of said amplifiers, a connection from the anode of said first amplifier to the grid of a second amplrifier, said connection including a condenser and a con nection between the cathode and grid of the second amplifier which is resonant to the frequency of the currents to be amplified, the

last mentioned connections in series with the condenser forming a; shunt circuit between the cathode and anode of the first amplifier.

2. The combination in an amplifying system of a pluralit of electron discharge amplifiers connecte in cascade, eac h' of which has a cathode, an anode and a grid, and plate and grid circuits, means for impressing currents which are to be amplified upon the grid circuit of one' of said amplifiers, shunt circuits connecting the anodes and cathodes of each amplifier of the series except the last, a portion of each of said shunt circuits having a low impedance for currents of the frequency to be amplified, another portion 'of each of said shunt circuits having a high impedance for currents of the frequency to be amplified, and a'much lower impedance for currents of lower frequencies, and means for impressing the potential variations set up across this portion of the shunt circuit upon the grid circuit of the next succeeding amplifier of the series.

3. The combination in an amplifying system of a series of electron discharge amplifiers, each of which has a cathode, an anode,

anda grid and plate and grid circuits, means for 1m the grld circuit of one of mid amplifiers,

high ohmic resistances in the plate circuits of said amplifiers, connections from each of the anodes of said amplifiers except the last tem of a plurality of electron discharge amplifiers connected in cascade, each of which has a cathode, an anode and a grid, and plate and grid circuits means for impressing currents which are to be amplified upon the grid circuit of one of said amplifiers, shunt circuits connecting the anodes and cathodes pressing currents to be amplified upon of each amplifier of the series except the last, a portion of each of said shunt circuits having a low impedance for currents of the frequency to be amplified, another portion of each of said shunt circuits having a high impedance for currents of the frequency to be amplified, and a much lower impedance for currents of other frequencies, and means for impressing the potential variations set up across this portion of the shunt circuit upon the grid circuit of the next succeeding amplifier of the series.

5. The combination in an amplifying system of a series of electron discharge amplifiers each of which has a cathode, an anode, and a. grid, and plate and grid cir cuits, means for lmpressing currents which are to be amplified upon the grid circuit of the first of said amplifiers, shunt circuits con necting the anodes and cathodes of each am plifier of the series except the last, each of i said shunt circuits comprising a condenser in series with a parallel circuit which is resonant to the frequency of the currents to be amplified, said resonant circuit being connected to the grid circuit of the next succeedingamplifier of the series.

6. The combination in a radio receiving system of a plurality of electron discharge amplifiers connected in cascade, each of which has a cathode, an anode and a grid, and plate and grid circuits, means for impresslng received impulses upon the grid circuit of the first, a detector having a local source of high frequency oscillations ass0 ciated therewith operatively related to the plate circuit of the last amplifierof the series, shunt circuits connecting the anodes and cathodes of each amplifier of the series, except the last, a portion of each of said shunt circuits having a high impedance for currents of the frequency to be amplified and a much lower impedance for currents of other frequencies, and means forimpressing the potential variations set up across this portlon of the shunt circuit upon the grid circuit ofthe next succeeding amplifier of the series.

7. The combination in an amplifying system of a. plurality of electron discharge am plifiers each of which has a cathode, an anode and a grid, and plate and grid circuits, means for impressing currents which are to be amplified upon the grid circuit of one of said amplifiers, high impedances in the plate circuits of said amplifiers, a direct connection through a condenser from the anode of the first amplifier to the grid of the second amplifier, and a parallel resonant circuit connecting the cathode and grid of the second amplifier, said resonant circuit belng tuned to the frequency of the currents to be amplified and forming in connection with the condenser a shunt circuit between the cathode and anode of the first amplifier.

8. The combination in an amplifying system of a series of electron discharge amplifiers each of which has a cathode, an anode and a grid, and plate and grid circuits, means for impressing currents to he amplified upon the grid circuit. of one of said amplifiers, high impedance in the plate circuits of said amplifiers, connections rom each of the anodes of the amplifiers except the last. of the series to the grid of the next succeeding amplifier, each of said connections including a condenser, a parallel resonant circuit c-on- 'ne-cted between the cathode and grid of each of said amplifiers which is tuned to the frequency of the currents to be amplified said resonant circuits forming in connection with the condensers shunt, circuits between the cathodes and anodes of the amplifiers, and a common connection between the cathodes of all of the amplifiers.

In witness whereof, I have hereunto set my hand this 10th day of February, 1919.

CHESTER W. RICE. 

